The invention will be described with particular reference to the detection and control of collusion in a game of multiplayer poker. It is to be clearly understood, however, that the scope of the invention is not limited to the detection and control of collusion in this particular game.
The game of poker is widely played in many jurisdictions, particularly in the United States of America. A traditional game of poker is a multi-player game in which, during each turn of the game, the players compete against each other to win an accumulated jackpot (“the pot”), to which all the players have contributed to some extent by means of wagers. It is clear that the game is a zero-sum game, as the gain of the winner of the pot is equal to the accumulated losses of the other players in the game. It is, however, also known for a party who arranges or hosts a game of poker to levy a commission (“a rake”) on the pot in order to derive revenue.
The game of poker is played at both land-based and on-line casinos, at the latter by means of a communication network such as the Internet.
Although there are many variations of the game of poker, the basic aim of the game is for each player to assemble five playing cards (“a hand”) from a deck of cards and to wager that their hand will outrank those of the other players, according to predetermined criteria. Once the players' hands have been assembled and wagers placed, the respective hands are compared (“the show down”) in order to determine the winning player, who wins the pot.
The winner is usually the player whose hand contains a highest-ranking desirable combination of five playing cards. The desirability of any combination of five playing cards in a hand is inversely proportional to the probability of assembling that particular combination of cards. Desirable combinations of playing cards are, given a standard deck of 52 playing cards, in order of increasing desirability: a pair of cards having the same rank (“one pair”); two pairs of cards in which the rank of each pair is different (“two pairs”); three cards having the same rank (“three of a kind”); “a straight” in which the five cards of a hand are in sequentially increasing rank order, with no restriction as to suite, “a flush” in which the five cards are all of the same suite; “a full house” in which three cards are each of the same rank, while the remaining two cards each have another identical rank; “four of a kind” in which four cards of the hand each have the same rank; “a straight flush” in which the five cards are in sequentially ascending rank order and are all of the same suite; and a “royal flush” in which the five cards are all of the same suite and are ranked Ace, King, Queen, Jack and 10. Where a deck is used that has fewer than 52 cards, the probability of assembling a full house is greater than that of being dealt a flush, making the latter combination of cards more desirable than the former.
The placement of wagers is achieved by one or more rounds of betting during the course of a turn of the game. The first player to act in a betting round can place a wager (“to bet”), withdraw from the turn of the game (“to fold”), or do nothing, merely passing the opportunity on to the next player (“to check”). After an initial bet, if there is one, the rest of the players, in turn, have the choices of increasing the size of the wager (“to raise”), folding, or matching the size of the previous wager (“to call”). A round of betting is completed when all the players who have not folded, and who will be referred to, for convenience, as the surviving players, have contributed the same amount to the pot. Any player who decides to fold does not participate any further in the particular turn of the game and forfeits all wagers he has made in that turn. To keep betting rounds from continuing indefinitely, it is customary for there to be at most three raises per betting round.
In each turn of the game, one player assumes the role of dealer of the playing cards. Betting is always done in a clockwise order. The first player to act is the one immediately clockwise of the dealer. Consequently, the dealer is the last to bet and, having seen the actions of the other players in the betting round, has access to the most information and is in a stronger position to the other players. For reasons of equity, the role of dealer passes to the next player in a clockwise direction after each turn of the game. When the game of poker is played in an on-line environment, the role of dealer is a symbolic one as dealing of cards is performed under software program control.
The size of bets or raises is determined by the rules of the game. A game of poker is characterised by the sizes of permissible bets. During the first two betting rounds, all bets and raises must be of a predetermined size (“the minimum bet”) and must be of another, but greater, predetermined size (“the maximum bet”) during the remaining betting rounds. Typically, the maximum bet is twice the minimum bet. A game in which the minimum bet is $5 and the maximum bet is $10 is characterised as a $5/$10 game.
At the start of a turn of the game, one or more players immediately clockwise of the dealer may be required to make bets (“blinds”) without having seen any cards, in order to ensure that there is always something in the pot. As an alternative, each player may be required to make an initial wager of a predetermined size (“an ante”).
It will be appreciated that the game of poker is a mixed game, combining elements of both chance and skill or strategy. It is known for two or more players in a poker game to co-ordinate their respective playing strategies in order to gain an advantage over the remaining players in the game, thereby destroying the fairness of the game.
Most variations of the game of poker fall into two main classes, namely draw poker and stud poker. In stud poker, one or more cards dealt to each player is visible to the other players in the game, while in draw poker, the cards in a players' hand are only revealed at the showdown stage of the game. Stud games also tend to have more betting rounds than draw poker, resulting in larger pots.
Within these two main classes, there are other variations that relate, mainly to the steps by which a player may assemble five playing cards in order to obtain the highest possible ranking hand. It will be further appreciated that the detection of collusion in a game of poker will depend, in part, upon the particular variation of the game being played. For the sake of clarity, the sequential steps relating to a number of the most popular variations of the game will be outlined below.    a) 5 Card Draw            1. Each player is dealt five cards face down        2. 1st Betting round        3. Each player may discard any one or more cards in his hand and draw replacement cards with the goal of improving his hand (“the draw”)        4. 2nd Betting round        5. Showdown (highest ranking hand wins the pot)            b) 5 Card Stud            1. A first card is dealt face down to each player        2. A second card is dealt face up to each player        3. 1st Betting round        4. A third card is dealt face up to each player        5. 2nd Betting round        6. A fourth card is dealt face up to each player        7. 3rd Betting round        8. A fifth card is dealt face up to each player        9. 4th Betting round        10. Showdown (highest ranking hand wins the pot)            c) Texas Hold 'Em            1. A first two cards are dealt face down to each player (“hole cards”)        2. 1st Betting round        3. A first three community cards are dealt face up (“the flop”)        4. 2nd Betting round        5. A fourth community card is dealt face up (“the turn”)        6. 3rd betting round        7. A fifth and final community card is dealt face up (“the river”)        8. 4th Betting round        9. Showdown (highest ranking hand made up of any combination of a player's two hole cards and the five open community cards)            d) Omaha            1. Four hole cards are dealt face down to each player        2. 1st Betting round        3. A first three community cards are dealt face up (the flop)        4. 2nd betting round        5. A fourth community card is dealt face up (the turn)        6. 3rd Betting round        7. A fifth and final community card is dealt face up (the river)        8. 4th Betting round        9. Showdown (highest ranking hand made up of any combination of two hole cards and three open community cards)            e) Omaha Hi/Lo
The procedural rules of this variation of the game of poker are identical to those of the Omaha variation, with the exception that, at the showdown, the pot is split 50/50 between the highest ranking hand made up of any combination of a player's four hole cards and the three open community cards, and a best qualifying low hand. A low hand must be “8 or lower” to qualify. Thus, any hand that contains a 9 or higher cannot qualify as a low hand. The winning qualifying low hand is determined firstly by the player with the lowest high card. Upon a tie, the hand goes to the player with the next lowest high card. If there is no qualifying low hand, the high hand wins the entire pot.    f) 7 Card Stud            1. All players ante        2. Two hole cards are dealt face down to each player        3. A third card is dealt face up to each player (“door card”)        4. 1st Betting round        5. A fourth card is dealt face up to each player (“Fourth Street”)        6. 2nd Betting round        7. A fifth card is dealt face up to each player (“Fifth Street”)        8. 3rd Betting round        9. A sixth card is dealt face up to each player (“Sixth Street”)        10. 4th Betting round        11. A seventh and last card is dealt face up to each player (“Seventh Street”)        12. 5th Betting round        13. Showdown (highest ranking hand made up of any combination of five of the player's seven cards        
On the first round of betting, the low card by suite is required to initiate action with a bet equal to half the lower table limit, the suites being ranked as spades, hearts, diamonds and clubs, from highest to lowest. On subsequent betting rounds, the highest exposed hand to date initiates betting action    g) 7 Card Stud Hi/Lo
The procedural rules of this variation of the game of poker are identical to those of the 7 Card Stud variation, with the exception that, at the showdown, the pot is split 50/50 between the best high hand and the best qualifying low hand. Each player can use any five cards in his hand for the high hand, and any five cards in his hand for the low hand.    h) Razz
The procedural rules of this variation of the game of poker are identical to those of the 7 Card Stud variation, with the exception that the lowest hand wins the pot. Each player can use any five of the seven cards in his hand for the low hand. Aces are low and straights and flushes have no effect on the value of the hand. The best possible low hand is 5-4-3-2-Ace.    i) Manila (2 card)
This variation of the game of poker is played with a reduced deck of 32 cards (sevens to aces), accommodating a maximum of 11 players.                1. Two hole cards are dealt face down to each player        2. A first community card is dealt face up        3. 1st Betting round        4. The next card in the deck is discarded (“burnt”)        5. A second community card is dealt face up (Fourth Street)        6. 2nd Betting round        7. The next card in the deck is burnt        8. A third community card is dealt face up (Fifth Street)        9. 3rd Betting round        10. The next card in the deck is burnt        11. A fourth community card is dealt face up (Sixth Street)        12. 4th Betting round        13. The next card in the deck is burnt        14. A fifth community card is dealt face up (Seventh Street)        15. 5th Betting round        16. Showdown (highest ranking hand made up of a player's two hole cards and the five open community cards)        
A system and method for detecting and controlling collusion in a multiplayer game is disclosed in applicant's co-pending application number PCT/US03/38068, which incorporated herein, in its entirety, by reference. The method includes the steps of continuously deriving, for each participating player, one or more statistics as a function of a total number of turns of the game played by the player and the outcomes of the wagers made by the player in these turns of the game; monitoring the statistics of each player; and, generating an output when any statistic of any player changes by more than a predetermined amount, the output being an indicator of possible collusion by that player.
The player statistics referred to in PCT/US03/38068 are statistics that relate to a single player. The applicant has found that there are instances of collusive play that are more easily detectable by means of more complex statistics.